class_docstr: Reader for corpora that consist of parenthesis-delineated parse trees,
  like those found in the "combined" section of the Penn Treebank,
  e.g. "(S (NP (DT the) (JJ little) (NN dog)) (VP (VBD barked)))".
code: def _normalize(self, t):
      # Replace leaves of the form (!), (,), with (! !), (, ,)
      t = re.sub(r"\((.)\)", r"(\1 \1)", t)
      # Replace leaves of the form (tag word root) with (tag word)
      t = re.sub(r"\(([^\s()]+) ([^\s()]+) [^\s()]+\)", r"(\1 \2)", t)
      return t
  
imports: import sys
  from nltk.corpus.reader.api import *
  from nltk.corpus.reader.util import *
  from nltk.tag import map_tag
  from nltk.tree import Tree
label_desc: Use image node_id 3 for calling the BracketParseCorpusReader obj's underlying member method code with example usage: obj._normalize(t) and returns: t